This invention relates to a system for feeding electricity to the ground coils of a superconductive magnetically levitated railway in which a train is equipped with superconducting magnets.
In one example of a system in this field of the art, a so-called ground primary-type levitated railway in which a vehicle is equipped with a field device includes propulsion coils disposed on a guideway and employs a feeder system in which the lengths of feeder sections are greater than the length of the train.
FIG. 1 is theoretical circuit diagram illustrating a dual-feeder system for feeding electricity to the ground coils of a superconductive magnetically levitated railway in the prior art.
As illustrated in FIG. 1, the system includes a first feeder line 1 and a second feeder line 2 supplied with electric power from a substation (not shown). The first feeder line 1 is connected to first feeder section 12 via a feeder-section switch 6 and to a first feeder section 14 via feeder-section switch 8, and the second feeder line 2 is connected to a second feeder section 13 via a feeder-section switch 7.
Numeral 18 denotes a superconductive magnetically levitated train having a length that extends substantially along the length of each feeder section 12. Accordingly, in this example the voltage applied to the ground coil opposing the superconducting magnet (not shown) of the train 18 is impressed upon one feeder section 12 so that the feeder voltage of the feeder section rises. For example, the length of the train 18 is 300 m and the length of the feeder section is 450 m.
If a propulsion-levitation-guide system or propulsion-guidance system is applied to the ground coils of a superconductive magnetically levitated railway, then, in accordance with the above-described system for feeding electricity, a high feeder voltage is applied to the guidance wiring (hereinafter referred to as "null-flux wiring"), which is installed in order to obtain the guidance force of the vehicle, that interconnects the ground coils disposed on mountain and ocean sides of the railway. This makes it necessary to take measures for insulating the null-flux wiring, as a result of which costs rise.
A propulsion-levitation-guide system or propulsion-guidance system applied to the ground coils of a superconductive magnetically levitated railway has already been disclosed in the specification of a U.S. Pat. No. 4,913,059 filed by the present applicant. Such a propulsion-levitation.-guidance system for the ground coils of a superconductive magnetically levitated railway will be described with reference to FIG. 2.
Ground coils for propulsion, levitation and guidance comprise a ground coil 20 and a ground coil 20', which are disposed respectively on both ocean and mountain sides of a superconductive magnetically levitated railway, and null-flux wiring 32 interconnecting the coils 20, 20'. The ground coils 20 include successively arranged U-, V- and W-phase coils 21, 22, 23 ..., and the ground coils 20' on the mountain side similarly include successively arranged U-, V- and W-phase coils ... opposing the U-, V- and W-phase coils 21, 22, 23 ....
The opposing U-phase coil 21 on the ocean side and U-phase coil on the mountain side are interconnected by the null-phase line 32. An AC U-phase power supply 30 is connected to the null-flux line 32 via an electric wire 31 so that U-phase voltage is applied to the U-phase coil 21 on the ocean side and to the U-phase coil on the mountain side. Though not shown, the V-phase coil 22 and W-phase coil 23 are similarly connected by null-flux lines so that V-phase and W-phase power supplies are applied to these null-flux lines. These coils are serially connected and arranged one after the other to form the first feeder section 12. Similarity, the second feeder section 13 comprising the U-phase coil 24, V-phase coil 25 and W-phase coil 26 is constructed.
By virtue of this arrangement, a propulsion force and levitating force can be obtained between the coils of each phase, which are disposed on both side walls of the superconductive magnetically levitated railway, and the superconducting magnets mounted on the train that travels along the railway while in opposition to the coils. In addition, a force that guides the train can be obtained by the coils of each phase and the null-flux lines.
A propulsion-guidance system for the ground coils of a superconductive magnetically levitated railway will be described with reference to FIG. 3.
As shown in FIG. 3, a ground coil for propulsion and guidance is formed on both the ocean and mountain side walls of a superconductive magnetically levitated railway. A ground coil 40 on the ocean side includes a successively arranged U-phase coil 41, V-phase coil (not shown) and W-phase coil (not shown). Similarly, a ground coil 40' on the mountain side includes a U-phase coil 41', V-phase coil (not shown) and W-phase coil (not shown) arranged to oppose the corresponding phase coils of the ground coil 40 on the ocean side.
The opposing U-phase coil 41 on the ocean side and U-phase coil 41' on the mountain side are connected by a null-flux line 52. An AC U-phase power supply 50 is connected to the null-flux line 52 via an electric wire 51 so that U-phase voltage is applied. Though not shown, the V-phase coil and W-phase coil are similarly connected by null-flux wiring so that V-phase and W-phase power supplies are applied. Numerals 19, 19' denote superconducting magnets mounted on the train. These are arranged so that they will oppose the U-phase coil 41 and U-phase coil 41' when the train runs.
It should be noted that the ground coils for levitation are laid independently on the railway bed between both side walls.
By virtue of this arrangement, a propulsion force can be obtained between the coils of each, which are disposed on both side walls of the railway, and the superconducting magnets mounted on the train that travels along the railway while in opposition to the phase coils. In addition, a force that guides the vehicle can be obtained by the coils of each phase and the null-flux lines.
Further, a levitating force is obtained by the ground coils for levitation laid independently on railway bed between both side walls, though this is not illustrated in the drawings.
The arrangement of one feeder section of a ground coil provided on one side wall of the superconductive magnetically levitated railway according to the prior art will be described next. It should be noted that the opposing ground coil and the null-flux wiring are deleted from the drawing.
As shown in FIG. 4, a plurality of coils 41, 42, 43, 44, .., 40+(N-3), 40+(N-2), 40+(N-1), 40+N branch from the U, V and W phases of the feeder lines, the U phases are serially connected via a section switch SW, and so are the V phases and W phases. In addition, the coils of the U, V and W phases are all connected to a neutral line N at their terminal ends TM. More specifically, the U, V and W phases are wye-connected to form one section, namely a feeder section. By way of example, the interphase voltage of the feeder lines is 22,000 V, and the voltage of the feeder lines to ground (namely the voltage between each phase and the neutral line N) is 22,000/.sqroot.3 V , or 12700 V.
In the system for feeding electricity to the ground coils of such a superconductive magnetically levitated railway, particularly in a case where the number of cars constituting a train is large so that there are a large number of superconducting magnets and it is necessary to feed electricity to a train of great length, the back emf of a linear synchronous motor rises when the train is running. As a result, the feeder voltage of the ground coils rises and there is a rise in the applied voltage for the null-flux wiring, thus making it necessary to provide greater insulation for the null-flux wiring and its terminals. This raises cost. If the system is operated over a long period of time, measures for dealing with a deterioration in insulation will also be necessary.
Further, when electricity is fed to the ground coils of the superconductive magnetically levitated railway with the conventional feeder system, the feeder voltage impressed upon the ground coils cannot be reduced at will.
Accordingly, an object of the present invention is to provide a multiplex feeder system of feeder sections for supplying electricity to the ground coils of a superconductive magnetically levitated railway, in which feeder sections serving as individual units are each constituted by a feeder section shorter than vehicle length in order to reduce the feeder voltage of the ground coils of the superconductive magnetically levitated railway, thereby making it possible to drive the superconductive magnetically levitated vehicle by a low feeder voltage.
Another object of the invention is to provide a multiplex feeder system of feeder sections for supplying electricity to the ground coils of a superconductive magnetically levitated railway capable of being applied to a propulsion-levitation- guidance configuration or a propulsion-guidance configuration by reducing the feeder voltage of the ground coils even in a system for feeding electricity to the ground coils of a superconductive magnetically levitated train of great length, and wherein the induced voltage of unit feeder sections is reduced, the multiplexing of feed of electricity is performed in an appropriate manner and there is no decline in reliability and durability when the feeder system fails.